Control method of a wind turbine generator

Abstract

The control method of a wind turbine generator increases the speed range of wind turbine generators, maximizing the operation and efficiency thereof, in addition to lengthening their service life, on minimizing the extreme and fatigue loads to which the wind turbine generators are subject, and which are due mainly to the stops and disconnections thereof as a result of strong gusts of wind. More specifically, the control method of the present invention stands out essentially for being based on the control of the reactive current circulating through the electric generator, said reactive current control being carried out in accordance with the rotational speed (ω g ) for the purpose of reducing the voltage at the converter terminals on the generator side, or rotor voltage (V R ), which ultimately allows a transitional increase in the speed range of the wind turbine generator.

The invention claimed is: 
     
       1. Control process of a wind turbine generator, said wind turbine generator comprising a wind rotor, at least two blades linked with said wind rotor, an electric generator, a control unit and a power converter connecting the electric generator to the grid, said control process comprising:
 a) determining a signal indicative of wind turbine generator rotational speed (ω g ); 
 b) establishing a first command (idref 1 , Qref 1 ) for reactive current and/or reactive power; 
 c) establishing a second command (idref 2 , Qref 2 ) for reactive current and/or reactive power; 
 d) comparing the signal indicative of rotational speed (ω g ) with a predetermined first speed limit, in order to act in accordance with one of the following substages: 
 d1) applying the first command (idref 1 , Qref 1 ) for controlling the generator in the event that the signal indicative of rotational speed (ω g ) calculated in stage a) is lower than the first speed limit value; and 
 d2) applying the second command (idref 2 , Qref 2 ) for controlling the generator in the event that the signal indicative of rotational speed (ω g ) calculated in stage a) is greater than or equal to the first speed limit value. 
 
     
     
       2. The control process of a wind turbine generator of  claim 1 , wherein the second command (idref 2 , Qref 2 ) is inductive. 
     
     
       3. The control process of a wind turbine generator of  claim 2 , wherein the stage d2) of applying the second command (idref 2 , Qref 2 ) for controlling the generator comprises the step of applying the second command (idref 2 , Qref 2 ) as the upper limit of the first command (idref 1 , Qref 1 ). 
     
     
       4. The control process of a wind turbine generator of  claim 1 , wherein the stage d2) of applying the second command (idref 2 , Qref 2 ) for controlling the generator comprises the step of switching to the second command (idref 2 , Qref 2 ) from the first command (idref 1 , Qref 1 ). 
     
     
       5. The control process of a wind turbine generator of  claim 3  wherein the second command (idref 2 , Qref 2 ) is calculated based on a predetermined inductive reactive power value. 
     
     
       6. The control process of a wind turbine generator of  claim 3 , wherein the second command (idref 2 , Qref 2 ) is dependent on the signal indicative of rotational speed (ω g ) and is calculated by means of a dependent function or table that relates the value of the first signal indicative of rotational speed (ω g ) to the appropriate value for the second command (idref 2 , Qref 2 ). 
     
     
       7. The control process of a wind turbine generator of  claim 1 , wherein the first command (idref 1 , Qref 1 ) is calculated based on a reactive power command or power factor, obtained from a voltage controller the parameters of which are configured in accordance with grid integration requirements. 
     
     
       8. The control process of a wind turbine generator of  claim 1 , characterised in that the signal indicative of rotational speed (ω g ) is the rotational speed (ω g ) itself measured directly at the generator axis, while the first limit value with which it is compared is, likewise, a speed value (ω lim1 ). 
     
     
       9. The control process of a wind turbine generator of  claim 1 , characterised in that the signal indicative of rotational speed (ω g ) is a voltage measurement made at the converter terminals on the generator side, or rotor voltage (V R ), the first limit value with which it is compared being a converter voltage limit value (V Rlim1 ). 
     
     
       10. The control process of a wind turbine generator, of  claim 1 , comprising:
 comparing the signal indicative of rotational speed (ω g ) with a predetermined second limit value greater than or equal to the predetermined first limit value; and 
 reducing the active power demanded from the electric generator by reducing torque when the signal indicative of rotational speed (ω g ) is greater than said second limit value. 
 
     
     
       11. The control process of a wind turbine generator, of  claim 1 , comprising:
 comparing a signal indicative of the temperature of at least one electric element connected between the electric generator rotor winding and the grid; and 
 reducing the active power demanded from the electric generator when the value of the signal indicative of the temperature of an electric element connected between the electric generator rotor winding and the grid is greater than said threshold temperature value. 
 
     
     
       12. Wind turbine generator operating according to the control process described in  claim 1 . 
     
     
       13. The control process of a wind turbine generator of  claim 4  wherein the second command (idref 2 , Qref 2 ) is calculated based on a predetermined inductive reactive power value. 
     
     
       14. The control process of a wind turbine generator of  claim 4 , wherein the second command (idref 2 , Qref 2 ) is dependent on the signal indicative of rotational speed (ω g ) and is calculated by means of a dependent function or table that relates the value of the first signal indicative of rotational speed (ω g ) to the appropriate value for the second command (idref 2 , Qref 2 ). 
     
     
       15. Wind turbine generator operating according to the control process described in  claim 2 . 
     
     
       16. Wind turbine generator operating according to the control process described in  claim 3 . 
     
     
       17. Wind turbine generator operating according to the control process described in  claim 4 . 
     
     
       18. Wind turbine generator operating according to the control process described in  claim 5 . 
     
     
       19. A control process of a wind turbine generator said wind turbine generator comprising a wind rotor, at least two blades linked with said wind rotor, an electric generator, a control unit and a power converter connecting the electric generator to the grid, said control process comprising:
 a) determining a signal indicative of wind turbine generator rotational speed (ω g ); 
 b) establishing a first command (idref 1 , Qref 1 ) for reactive current and/or reactive power; 
 c) establishing a second command (idref 2 , Qref 2 ) for reactive current and/or reactive power; 
 d) comparing the signal indicative of rotational speed (ω g ) with a predetermined first speed limit, in order to act in accordance with one of the following substages: 
 d1) applying the first command (idref 1 , Qref 1 ) for controlling the generator in the event that the signal indicative of rotational speed (ω g ) calculated in stage a) is lower than the first speed limit value; 
 d2) applying the second command (idref 2 , Qref 2 ) for controlling the generator in the event that the signal indicative of rotational speed (ω g ) calculated in stage a) is greater than or equal to the first speed limit value, 
 e) calculating the time interval during which rotational speed (ω g ) is greater than the first speed limit value; 
 f) comparing said calculated time interval with a predetermined maximum time interval; and 
 g) disconnecting the wind turbine generator in the event that said time interval is greater than the predetermined maximum time interval. 
 
     
     
       20. The control process of a wind turbine generator of  claim 19 , further comprising:
 comparing rotational speed (ω g ) with a predetermined second speed limit value (ω lim2 ) greater than the first speed limit value (ω lim1 ); and 
 disconnecting the wind turbine generator in the event that rotational speed (ω g ) is greater than the second speed limit value (ω lim2 ).